Method and apparatus for submerged well drilling



Feb. 26, 1957 w. E. GILBERT 2,733,027

METHOD AND APPARATUS FOR SUBMERGED WELL DRILLING Filed April 20. 1954 4Sheets-Sheet. 1

INVENTQQ;

WALTON E.. GILBERT.

ms AGENT Feb. 26, 19577 w. E. GILBERT METHOD AND APPARATUS FOR SUBMERGEDWELL DRILLING Filed April 20, 1954 4 Sheets-Sheet 2 INVENTORz Illu..-.IIJ-l WALTON E. G|LBERT BY: M714 Q HIS AGENT Feb. 26, 1957 w. E.GILBERT 2,783,027

METHOD AND APPARATUS FOR SUBMERGED WELL DRILLING Filed April 20, 1954 4Sheets-Sheet 3 lNVENTOR- WALTON E. GILBERT HXWCQA? BY HIS AGENT Feb. 26,1957 w. E. G|LBERT 2,783,027

METHOD AND APPARATUS FOR SUBMERGED WELL DRILLING Filed April 20, 1954 4Sheets-Sheet 4 mvENTon;

l ms AGENT FIG. 6

FIG.5

WALTON E GILBERT United States Patent O METHGD AND APPARATUS FORSUBMERGED WELL DRILLING Walton E. Gilbert, New York, N. Y., assigner toShell Development Company, New York, N. Y., a corpora tion of DelawareApplication April 20, 1954, Serial No. 424,342 Claims priority,application Netherlands April 24, 1953 10 Claims. (Cl. 2552.5)

This invention relates to the drilling of oil Iand gas wells andpertains more particularly to a method and apparatus for drilling wellsin areas covered by water to a depth of 300 feet or more.

In drilling oil and gas wells in areas covered with water, use has beenmade inthe past of different types of constructions, such as drillinginstallations installed on sinkable vessels or barges, installationsbuilt on piles, artificial islands and similar structures which findsupport on the bottom while drilling wells. However, the use of theseconstructions is limited to water of shallow depth.

lt is, therefore, 'the principal object of the invention to provide amethod and apparatus for drilling wells in water at greater depths.

Another object of this invention is to provide a method and apparatusfor drilling wells in land covered by deep water by employing drillingapparatus which is supported in or on the water throughout the drillingoperations.

A further obiect of the present invention is to provide a method andapparatus for the directional drilling of a well in submerged land froma ioating base positioned thereabove.

To this end, according to the invention, a curved outer casing is usedwhich extends from a point near the water level where it is `almosthorizontal to the bottom where it has a vertical or inclined positionand into which drill pipes and other equipment are run. This outercasing,

f which forms the part of the well lying above the bottom of the water,is therefore employed as a guide tube for the drilling string and bit,inner casing strings, etc. During ythe drilling of wells, the upper partof the outer casing o-r guide tube is connected to a barge carrying thedrilling installation which must be adapted to be positioned to operatein the almost 4horizontal direction in which the drilling tools must beinserted into the guide tube and pulled therefrom.

Figure l is a sideelevation of the curved guide tube which is in afloating position and is ready :to be placed.

Figure 2 is a side-elevation of the guide tube after its lower end hasbeen brought in contact with the bottom and the upper end has beenconnected to the barge carrying the drilling equipment.

Figure 3 is a plan view corresponding to Figure 2.

Figures 4, 5 and 6 show the various stages of anchoring the guide tube.i

Figures 7 and 8 show the uppermost part of the guide tube in twosections which are at right angles -to each other.

.Figure 9 shows an elevation of this part after completion ofthe well.

When the present invention is employed in drilling operations, extensiveuse is made of techniques which are also employed in conventionaldrilling practice and the following description is therefore restrictedmainly to those parts of the method of operation and equipment whichdiiier from those normally employed. rThus, the actual drillingoperations and completion of the part of the well below the bottom ofthe water is carried out in ICC the usual way and therefore is notdescribed in detail herein. The part of the well which differs from thatnor molly employed is situated above the bottom of the water. This part(Figures 1, 2, 3) consists lof a curved outer casing or guide tube 1composed oi a series of sections 2, 3, 4, 5 and 6. These sections, whichmay be prebent in the desired form, have suiicient strength and are sohandled as to ensure that the elastic limit is not exceeded when theyare interconnected, transported and placed into position. The buoyancyot' floats 7, 8, 9 and 10 connected to the guide tube must exceed :theWeight of the guide tube and its appurtenances, e. g., a drill string tobe lun therethrough by a sufficient margin to ensure'that incidentalchanges of this weight, as for example, while running or removing drillpipe during the drilling process, will not affect essentially the formof the guide .tube which is supported by means of iloats. insofar as thebuoyancy of iloats S, 9 and lll) exceeds the weight of the guide tubeconnected thereto, it is absorbed as tension by anchor cables 12, 13,14, 15 and i6 held by anchors 17, 18, 19, 20 and 21.

Actual drilling operations are preceded by investigations leading toselection of a drilling site. On the selected site soundings are made todetermine the depths and the nature of the water bottom, while themovements of the water (tides, waves) which occur are also studied sincethe information thereby obtained is of importance to the constructionand location of the curved guide tube.

Sections 2, 3, 4, 5 and 6 of this guide itube,'often prebent in thedesired form, may be towed as separate floating units to .the drillingsite where they are interconnected at or above the surface of the waterby means of tlanges, couplings, or in any other manner and lowered, carebeing taken to ensure that no section is stressed beyond its elasticlimit. Anchors 17, 18, 19, 20 and 21 may be,

constructed in the form of open-top tanks which are towed, ortransported to the drilling site where they are connected by means ofcables to the tube sections 2, 3, 4, 5 and 6 and the iloats 7, 8, 9, 10and 11, after which the anchors are weighted with ballast material, forinstance, sand. As shown in Figures 5 and 6, a hose 23 may be usedwhich, by means of line 24- passing over pulley 2S and axed to theanchor, may be moved with its end to a point above said anchor so as `tofill the latter with the sand 59 to be discharged from a barge 60.

The floats as indicated in Figure 4 may each be constructed in the formof a hollow, internally-reinforced sphere fitted at its top with arailed platform 26 which provides working space for a diver handling theopening or closing of .the valves, the fixing of cables and the carryingout of similar operations. in Figures 4 and 5 each of cables 27, 28 and29 is connected to a separately controlled winch carried by barge 39.Ancho-r cable 27' is employed for lowering anchor 20, cable 28 forlowering iioat 9 and cable 29 for lowering a section of the curved guidetube. To ensure proper lowering, the buoyancy of the oat can becounterbalanced by expelling air from the lloat by means of waterintroduced as through a conduit or hose 61, :the tube section beingmeanwhile supported by the barge 30. When anchor Ztl has reached thebottom and is weighted with ballast S9 and the tube section and thefloat have been lowered to its propel' depth, the cables 27 and 29 arexed to the 'oat aft the points 31, the buoyancy of the float beingrestored by expelling the water present therein by means of air suppliedthrough hose 62. Care is thereby taken to ensure that the final airpressure in the iioat slightly exceeds the mean hydraulic pressure towhich the iioat is subjected. In order to synchronize the loweringoperation of the various sections with anchor and oat, each of thesesections may require a separate vessel.

Float 7 (Figure 3) consisting of two spheres, is employed to support theuppermost section 6 of the guide tube when, for instance, owing to roughweather, it is advisible to discontinue drilling operations temporarilyand when the well is completed. Float 1:1 is used to assist in keepingsection 2 alloa-t and in bringing it into place, whilst floats 8, 9 and10, situated at depths below the surface which are sufcient to preventsenious disturbance by the action of the waves, continuously exert anupward force. Each float may be provided with a mast 63 for aid invisually checking their alignment and marking the site of the well.Section of the guide tube is held by a cable secured to the top of thefloat and passing through a tubular opening which extends through float8.

In a typical case, such as that a present described, the sea may be 150meters or more deep and the guide tube 1 may consist of 10%" 13%"diameter casing depending on thte number of casing strings to beinserted and the depth at which the producing layer is expected. Thewall thickness is so chosen that the compressive stresses are keptwithin certain safe limits, thereby taking into account the wellpressures to be expected. The w-all thickness of each section of theguide tube 1 may be equal throughout the length of the section, or itmay be sub- Y stantially thicker in the center of the sections than atthe ends thereof, as illustrated. In the constructions shown in whichthe support of the guide tube 1 is concentrated at certain points, thistube is assembled of tapered sections which are hinged to the supportcables midway, thus ensuring that the support given by the floats andthe vessel is properly distributed over the length of the tube, andexcessive local curvature of the tube owing to movements of the vesselcaused by the action of wind and waves is prevented. Various means wellknown in the art may be applied for appropriate stitfening of theguidetube sections. Figures 7 and 8 show the manner in which a stifeningmade up of welds is constructed around guide tube 1. Circular plates 32provided with radial slots and a central hub 33 are slid into thedesired position and secured onto the tube by means of half cylinders.Longitudinal plates 35 are then mounted and welded in place, thusproviding a continuous reinforcement and supporting structure for thetube from plate 69 which is removably secured to the hull 41 of thebarge as shown in Figure .9.

When drilling and well servicing operations are carried out, tubesection 6 (Figures 3 and 4) is fixed to the barge 36 and will, forinstance, have a length of 30 to 60 meters. If the barge is lying incalm water this section 6 slopes downwards away from the barge at anangle varying between, say, 5 and 10 from a horizontal plane so as tominimize the length of the section affected by the action of the waves.This angle also facilitates the insertion of the drill pipe 70, drillbit 71 and casing in the guide tube. Y

Barge 36, which should preferably have a length of more than about 70meters to minimize pitching motion and to ensure easier insertion andextract-ion of pipes, is provided with a central ramp 37 aligned withsection 6 at the point of attachment of the latter to the barge. In thebow of the barge this ramp ends in a space 38 which will herein bereferred to as a cellar since its function is similar to that of acellar in a vertically drilled well. At the end of the cellar 38 a roundopening is provided in the ships side 41 through which the well-head orguide tube extends, which forms a water-tight connection with the barge.The rear end ofthe cellar is formed by a bulkhead 40 with a door which,when closed, makes the cellar into a compartment separated from theremaining part of the vessel to above the water line and, when the dooris open, the cellar 38 and the ramp 37 are in unobstructed communicationwith each other. The greater part of the drilling operations may becarried out through an opening in the door for inserting and pulling outpipes, it being possible to close this opening (if the cellar istemporarily submerged) by a hydraulically operated shutting-off deviceof the type conventional in blow-out preventers.

The barge is moored in alignment with the part of the well which isunder water and is kept in alignment by means of mooring cables andWinches which may, for instance, be operated from the bridge of barge36.

The barge is further equipped with derrick cranes 64 in the forecastle,the booms of which can be swung outside the bow of the barge so thatthey can support the wellhead, place it in position and connect it tothe vessel, disconnect it again and set the wellhead on cradle float 7.For this purpose section 6 may be provided with the necessary hooks orother gripping devices. If the barge is otherwise rigged for rotarydrilling the tools and parts employed in vertical drilling will have tobe adapted to drilling in a practically horizontal direction.

Figure 9 shows, partly in elevation and partly in section, the head of acompleted owing well which is situated in the barge and is ready forremoval to cradle oat 7. This figure may also be taken to illustrate theupper end assembly in place, at the commencement of drilling except thatthe casing spool 42, in which tube 1 is landed, would then be the onlyessential wellhead litting in place and the bell 43 of course would beremoved. The primary purpose of this bell is to protect the wellheadattachments against damage particularly during placement and removal ofthe head to and from the hull 41.

The drill pipe 70 in the curved guide tube is not only subjected to thetensile and torque stresses set up in vertical drilling but in this casereverse bending stresses are also exerted on it, thereby shortening itsservice life. Since the bending stresses are, however, inverselyproportional to the radius of curvature of the curved guide tube theymay be kept within safe limits justified from the economical point ofview by a proper selection of the radius of curvature. However, in somecases the radius of curvature thus determined may not permit a fullquarter circle between the water surface and the bottom of the water. Insuch cases the hole enters the bottom at an angle and directionaldrilling ensues to bring the bore to the angle of penetration desired.

The decision as to the type of entry to be used depends upon localconditions including water depths, tides, currents and weather.

In the system described, very high speeds of rotation should be avoidedso as not to curtail the life of the drill pipe 70 too much and toprevent vibrations in the guide tube, although rotational speeds of R.P. M. will in most cases be permissible. ln order to minimize vibrationsspecial care should also be taken to avoid bent drillpipe lengths andmisalignment between adjacent lengths of drill pipe or casing.

The method may be employed for drilling wells to depths of more than3,000 meters and when using a l1/ drill pipe, the minimum radius ofcurvature which can economically be used is about meters, so that forsea depths of less than 150 meters, inclined drilling into the bottomand directional drilling may be necessary.

The invention renders it possible to put the well on production beforethe wellhead is released from the barge and transferred to the cradlefloat. In this case the annulus remaining between guide tube 1 and thecasing, hung in the casing spool 46, serves as part of the flow line, i.e., as far as olf-take connection 47 (Figure 2) which is situated at asulcient distance from the wellhead so that, when the latter is removedfrom the cradle oat 7, this off-take connection and the pipelineconnected thereto remain undisturbed.

In the embodiment of Figure 9 the tubing is fastened in the tubinglanding head 48 and the oil is discharged via master gate 49, cross 50,flow valve 51, xed bean 52 and thence to the annulus which is formedwith offtake connection 47 as stated above. In some cases the bean maybe located at the position of the oli-take connection 47. In order tomake it absolutely certain that no cement remains in the latter space,it is advisable :to backwash this space immediately after cementing thecasing string by introducing water at 44 and withdrawing it at 47.

I claim as my invention: f

l. Apparatus for drilling offshore wells into earth formations coveredby a large body of water, said apparatus comprising a drilling vessel,drilling equipment including a drill string positioned on said vessel,an elongated substantially rigid guide tube in communication between thevessel and the earth formation below the body of water for conductingthe drill string and its bit from said vessel to and from saidformation, said guide tube extending from said vessel in a substantiallyhorizontal position and forming a substantially rigid support meanscontinuously curved so as to contact the formation at an angle of nogreater than 45 degrees to the vertical.

2. Apparatus for drilling offshore wells into earth formations coveredby a large body of water, said apparatus comprising a drilling vessel,drilling equipment including a drill string positioned on said vessel,an elongated substantially rigid guide tube in communication between thevessel and the earth formation below the body of water for conductingthe drill string and its bit from said vessel to and from saidformation, said guide tube extending from said vessel in a substantiallyhorizontal position and form ing a substantially rigid support meanscontinuously curved so as to contact the formation at an angle of nogreater than 45 degrees to the vertical, and oat means secured to saidguide tube for suspending it within said body of water.

3. Apparatus for drilling offshore wells into earth formations coveredby a large body of water, said apparatus comprising a drilling barge,drilling equipment including a drill string positioned on said barge, anelongated sub stantially rigid curved guide tube in communicationbetween the barge and the earth formation below the body of water forconducting the drill string and its bit from said barge to and from saidformation, said guide tube extending from said barge in a substantiallyhorizontal position and forming a substantially rigid support meanscontinuously curved throughout the major portion of its length so as tocontact the formation at an angle of no greater than 45 degrees to thevertical, and a plurality of float means secured to said guide tube forsuspending it within said body of water.

4. Apparatus for drilling offshore wells into earth formations coveredby a large body of water, said apparatus comprising a drilling barge,drilling equipment including a drill string positioned on said barge, anelongated substantially rigid curved guide tube in communication betweenthe interior of the barge and the earth formation below the body ofwater for conducting the drill string and its bit from said barge to andfrom said formation, said guide tube extending from said barge in asubstantially horizontal position and forming a substantially rigidsupport means continuously curved throughout the major portion of itslength so as to contact the formation at an angle of no greater than 45degrees to the vertical, and a plurality of anchored iioat means securedto said guide tube at spaced points therealong for suspending said guidetube within said body of Water.

5. Apparatus for drilling offshore Wells into earth formations coveredby a large body of water, said apparatus comprising a drilling barge,drilling equipment including a drill string positioned on said barge, anelongated substantially rigid curved guide tube in communication betweenthe interior of the barge and the earth formation below the body ofwater for conducting the drill string and its bit from said barge to andfrom said formation, said guide tube extending from said barge in asubstantially horizontal position and forming a substantially rigidsupport means continuously curved throughout the major portion of itslength so as to contact the formation at an angle of no greater than 45degrees to the vertical, and

a plurality of anchoredv float means' secured to said guide tube forsuspending it within said body of water, said guide tube comprising aplurality of sections connected end to end toforrn said guide tube, eachof said guide tube sections being secured to one of said float means atsubstantially the mid-point of each section.

6. Apparatus for drilling offshore wells into earth formations coveredby a large body of water, said apparatus comprising a drilling barge,drilling equipment including a drill string positioned on said barge, anelongated substantially rigid curved guide tube in communication betweenthe interior of the barge and the earth formation -below the body ofwater for conducting the drill string and its bit from said barge to andfrom said formation, said guide tube extending from said barge in asubstantially horizontal position and forming a substantially rigidsupport means continuously curved throughout the major portion of itslength so as to contact the formation at an angle of no greater than 45degrees to the vertical, and a plurality of anchored float means securedto said guide tube for suspending it within said body of water, saidguide tube comprising a plurality of sections connected end to end toform said guide tube, each of said guide tube sections being secured toone of said oat means at substantially'the mid-point of each section,the cross-sectional thickness of each section being a maximum value atthe mid-point of each section and tapering toward each end of thesection.

7. Apparatus for producing offshore wells drilled into earth formationscovered by a large body of water, said apparatus comprising a curvedwell casing curving from a substantially horizontal position above thesurface of the water to a substantially vertical position where thecasing contacts the formation below said body of water, a curved guidetube surrounding the well casing from the point where the casing entersthe formation to the surface of the body of water, valve means closingthe top of the well casing and controlling the ilow of fluid from thewell, and float means secured to said guide tube for suspending theguide tube within said body of water wherebythe valve means on said wellcasing is positioned above the surface of the water.

8. Apparatus for producing offshore wells drilled into earth formationscovered by a large body of water, said apparatus comprising a curvedwell casing curving from a substantially horizontal position above thesurface of the water through an arc of at least 45 degrees into coutactwith the formation below said body of water, a curved guide tubesurrounding the well casing from the point where the casing enters theformation to the surface of the body of water, valve means closing thetop of the well casing and controlling the flow of uid from the well,and float means secured to said guide tube at spaced points therealongfor suspending the guide tube within said body of water whereby thevalve means on said Well casing is positioned above the surface of thewater.

9. In a method of drilling off-shore wells into earth formations coveredby a large body of water by means of a rotatable string of drill pipe,the steps of disposing one end of said drill pipe in a substantiallyhorizontal position, supporting said end above the surface of saidwater, and guiding the remainder of said drill pipe through an Varc ofat least 45 degrees until the other end of said drill pipe contacts theformation below the body of water.

l0. In a method of drilling off-shore wells into earth formationscovered by a large body of water by means of a rotatable string of drillpipe, the stepsy of disposing one end of said drill pipe in asubstantially horizontal position, supporting said end above the surfaceof said water, gui-ding the remainder of said drill pipe through an arcof at least 45 degrees, maintaining the other end of said drill pipe incontact with the formation below the body of water, and suspending thecurved section of said drill pipe in said body of water.

(References on following page) References Cited in the le of this patentUNITED STATES PATENTS 8 Bean et al. Dec. 14, 1943 Lang July 19, 1949McNeill Aug. 5, 1952 Curtis et al July 7, 1953 Johnson Apr. 27, 1954

